1. Field of the Invention
The present invention relates to a PT (push-to) service and, more particularly, to a PT service system and method capable of enhancing service quality by transmitting and processing a talk burst request message.
2. Description of the Related Art
A PT service, which is intended to provide rapid communications for service providers and consumers of mobile network, is a communication service in which one client transmits media data (talk burst) to one or more other clients with which a session has been established. A PT service can be a push to talk (PTT) service for transmission of voice (audio) data, a push to view (PTV) service for transmission of moving picture (video) data, or a push to data (PTD) service for transmission of data. The PT service allows communication with a single recipient (1-to-1) or between groups of recipients as in a group chat session (1-to-many), and uses a session initiation protocol (SIP) to establish a session.
In a PT service system, a PT client (e.g., a client supporting a PT service) that wishes to transmit media data must first have an authority/permission to transmit the media data. Thus, prior to the actual transmission of the media data (talk burst), the PT client that wishes to transmit the media data transmits a request for a talk burst (a talk burst request message) to an associated PT server. In response to the talk burst request message, the PT server may transmit a talk burst granted message to the PT client. Once the PT client receives the talk burst granted message indicating that the PT client currently has the talk burst, then the PT client may perform the talk burst by transmitting the media data. This process is illustrated in FIG. 1.
More specifically, FIG. 1 illustrates the construction of a PT service system according to a background art. As shown in FIG. 1, the PT service system includes PT clients 21, 22, 23 and 24 each included in a mobile terminal and calling (paging) a PT service, and a PT server 10 which controls various functions of the system.
In this example, the first to fourth clients 21-24 are participating in a conference. The first PT client 21 obtains a talk burst and the second to fourth clients 22-24 are listening to the first PT client 21.
While the first PT client 21 is performing the talk burst (e.g., transmission of voice, video, or data), the other PT clients 22-24 each can transmit a talk burst request message to the PT server 10 in order to obtain a next talk burst following the first PT client 21.
Upon receiving the talk burst request messages from the PT clients 22-24, the PT server 10 places the talk burst request messages in a queue in the order of the reception and authorizes the talk burst in the order of the queue placement. For instance, if the PT server 10 receives the talk burst request messages from the second, the third and the fourth PT clients 22-24 in that order, then the PT server 10 gives the talk burst in that same order, i.e., the second, the third and then the fourth PT client. No time information is included in the talk burst request message according to the background art.
The talk burst request messages are transmitted to the PT sever 10 through a user datagram protocol (UDP) based on a RTCP (real time transport control protocol) for real time processing.
Namely, in the case that the talk burst request message is transmitted by using an unreliable UDP or if handoff occurs according to the movement of the PT clients, the talk burst request messages transmitted by the PT clients can be lost. In this respect, the related art PT service system does not define a solution for this case where the talk burst request message(s) transmitted by the PT client(s) are lost. This is a problem because, if the talk burst request message is lost, reliability of the service to the client and user service quality are degraded.
In addition, if the talk burst request messages transmitted by the PT clients are delayed in transmission due to a network load, reliability of the PT service is also degraded.